WEDNESDAY, July 17 (HealthDay News) -- One of every 50 prescriptions for addictive prescription painkillers in the United States is filled for so-called "doctor shoppers" who obtain the drugs for recreational use or resale on the street, a new study finds.

Although doctor shoppers make up less than 1 percent of all patients who bought painkillers in 2008, they purchased an estimated 4.3 million prescriptions for opioid drugs such as Oxycontin or Vicodin, the researchers found. That amounts to about 4 percent of all of this class of narcotic sold by weight that year.

"There's a hole in our prescription control system in the United States," concluded study co-author Douglas McDonald, a researcher with Abt Associates Inc., a think-tank located in Cambridge, Mass. "Lacking a universal health record, doctors have to rely on what patients tell them about what they've been prescribed by other doctors."

That means that "doctor shoppers can get multiple prescriptions for the same drug if they lie to their physician," he said.

The study, published July 17 in the journal PLoS One, constitutes the first national estimate of doctor shopping in the nation, the authors said.

Abuse of prescription medications has become a serious threat to public health in recent years. Between 1995 and 2011, admissions to emergency departments for opioid misuse increased about 10-fold, the authors noted in background information. Opioid overdose deaths rose from about 4,000 in 1999 to more than 16,600 in 2010 and are now twice as common as heroin and cocaine overdose deaths combined.

"It is a public health epidemic, and we don't really have a system in place to mitigate this or prevent it," McDonald said.

In the study, he and his colleagues analyzed a nationwide sample of more than 146 million opioid prescriptions dispensed during 2008. Besides Oxycontin and Vicodin, opioids include morphine, Percocet and Dilaudid.

One of every 143 patients who purchased opioid painkillers received a suspiciously large number of prescriptions from multiple prescribers, researchers found. On average, these patients used 32 prescriptions from 10 different doctors to obtain painkillers.

Some states have adopted prescription drug monitoring programs, but the patchwork nature of these efforts has rendered them ineffective, said Steve Pasierb, president and CEO of The Partnership at Drugfree.org.

Shoppers simply go from doctor to doctor and pharmacy to pharmacy until they receive the prescription they want and have it filled, Pasierb said. And because the monitoring programs function at the state level, all they have to do is cross state lines to avoid detection.

"I could have gotten a prescription in Portland yesterday, and then come to Connecticut and get another prescription," Pasierb said.

These monitoring programs also rely on doctors to access the data and use it when writing out a prescription.

"The data are there, but the physician has to pick up the phone and ask if the patient they are about to see already has a prescription," study co-author McDonald said. "The existing system relies on physicians adding that extra step to their fast-paced work schedule."

On top of that, some doctor shoppers have adopted very sophisticated techniques. "There are patients who have doctored MRI results, they go from doctor to doctor and show this falsified MRI record that shows they have a bone spur in their neck and they are in intense pain," McDonald said. "Addicts in general can be extremely good manipulators when they want to get their drugs."

Pasierb said for a prescription-monitoring program to truly be effective, it will have to be a nationwide network receiving prescription data from all states in real time. In addition, doctors would need to be legally required to use it.

Absent that, physicians can help prevent doctor shopping by screening new patients for their risk of abuse and by monitoring patients' adherence to prescribed treatments, the study's authors wrote.

"They need to do a better job screening, but they don't have the tools," Pasierb said of physicians. "Most doctors get no education in medical school about addiction. Their oath is to help this person, but they don't want to be the inspector general. They are time-challenged and they are loath to challenge patients."